Bile Cell-Free DNA as a Tumor-Proximal Source for Molecular Profiling of Biliary Tract Cancer: A Systematic Review and Meta-Analysis.

BACKGROUND

Molecular profiling is increasingly required for treatment selection in advanced biliary tract cancer, yet tumor tissue is often insufficient and plasma circulating tumor DNA has limited yield. Because bile directly contacts the biliary epithelium and is obtainable during routine biliary interventions, bile cell-free DNA (cfDNA) may provide a tumor-proximal molecular profiling source.

OBJECTIVE

We systematically reviewed and quantitatively synthesized bile cfDNA detection and profiling in biliary tract cancer.

METHODS

PubMed, EMBASE, and the Cochrane Library were searched from inception to 13 October, 2025 for studies that included at least ten patients with suspected or confirmed biliary tract cancer and extractable bile cfDNA outcomes. Pooled proportions were estimated using random-effects models with Freeman-Tukey double-arcsine transformation. Bile-versus-plasma detection was compared using pooled log risk ratios. Heterogeneity was quantified by I2, with a 95% prediction interval for the primary conservative estimate. Risk of bias was assessed with the Quality Assessment of Diagnostic Accuracy Studies-2 tool.

RESULTS

Eight studies including 271 patients with biliary tract cancer were included. After excluding two cohorts with 100% detection, the conservative pooled bile cfDNA molecular detection rate was 59.1% (95% confidence interval [CI] 49.0-68.7; I2 = 50.4%) with a 95% prediction interval of 33.3-82.5%. Bile cfDNA showed higher molecular detection than plasma cfDNA in within-study comparisons (risk ratio 1.58, 95% CI 1.19-2.10; I2 = 0%), with directionally higher allele fractions in bile. Bile-tissue concordance was 82.7% (95% CI 69.1-93.5; I2 = 43.7%). Among patients with non-diagnostic biliary cytology, incremental molecular detection yield was 36.6% (95% CI 26.9-46.9; I2 = 0%). Potentially actionable FGFR2 fusions, IDH1 mutations, and ERBB2 alterations were reported across five studies but were summarized descriptively because actionability definitions and reporting units varied.

CONCLUSIONS

Bile cfDNA showed higher molecular detection than plasma cfDNA and supported molecular profiling when tumor tissue was insufficient, but detection and endpoint heterogeneity limit its use as a stand-alone diagnostic test. Its role is best defined as opportunistic molecular profiling during indicated biliary procedures, pending prospective multicenter validation with standardized protocols.

PROTOCOL REGISTRATION: PROSPERO CRD420251250742 (registered prospectively prior to study conduct).